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Tektronix 1A1
50 MHz dual channel amplifier
1A1 front view

Compatible with 500-series scopes

Produced from 1964 to 1975


Manuals – Specifications – Links – Pictures

The Tektronix Type 1A1 plug-in for the 500-series scopes has two channels and a −3 dB point of 50 MHz at 50 mV/Div, 28 MHz at 5 mV/Div, and 2 Hz to 15 MHz at 500 μV/Div when channels 1 and 2 are cascaded. It was designed by Ron Olson.

There were three distinct versions of 1A1.

  • The first version, from 1964 to 1966, has a Nuvistor front-end, and rotary input switches that were concentric with the BNC jacks. The knobs to invert the input channels are concentric with the vertical position knobs.
  • The second version, from 1966 to ??? has fluted round V/cm knobs, and lever switches. The channel inversion control is an organ-style pull-push knob. The nuvistors are mounted under a thermal cover on a sub-chassis with rubber stand-offs.
  • The third model, from ??? until the end has four-sided V/cm knobs and a FET front-end.

Type 1A1 uses the "ALT SWEEP SLAVE PULSE" signal that is sent by scopes on pin 7 of the plug-in connector. In a Type 547 mainframe, this signal allows channel 1 to be displayed using the "A" timebase and channel 2 using the "B" timebase. This is useful, for example, to view the IF and AF of a radio receiver at the same time. Even after the front-end transitioned from Nuvistors to FETs, the output amplifier continued to use Nuvistors.

Type 1A1 has an External Trigger output for mainframes prior to the 547 that don't support plug-in triggering, and supplies the trigger system on pins 4/5 of the mainframe interface. It also has a ×10 amplified output from channel 1 that can be cascaded into the channel 2 input for 500 μV/Div sensitivity at reduced bandwidth (15 MHz).

Types 1A1 and 1A2 were introduced together in 1964, the former for high-end use, the latter as an upgrade/replacement for Type CA. Both remained available until the 500-series scope line was discontinued.

The 1A1 is not a perfect superset of the 1A2; it supplies external trigger from channel 1 only.

The 1A1 may have evolved from the Type J, which never went into production.

Key Specifications

Bandwidth 50 MHz @ 50 mV/Div and up (in fast mainframes), 28 MHz @ 5 mV/Div, 15 MHz with cascaded channels (~0.5 mV/Div)
Rise time 7 ns @ 50 mV/Div and up (in fast mainframes), 13 ns @ 5 mV/Div, 24 ns with cascaded channels (~0.5 mV/Div)
Deflection 5 mV/Div to 20 V/Div, 1−2−5
Max. input 600 V DC + peak AC
Input impedance 1 MΩ // 15 pF
Modes Ch 1, Ch 2, ALT, CHOP, ADD



Some Parts Used in the 1A1

Page Class Description Used in
7586 Vacuum Tube (Triode) Nuvistor triode 1A1 1A2 1A5 10A2 10A2A 11B1 11B2A M 321 321A 3A74 3T77 6R1A 3A1 3A3 3A5 3A6 3A8 3A74 3S76 3T77A 4S1 6R1 82 86